A theoretical analysis of the thermal conductivity of hydrogenated graphene

We investigate the thermal conductivity of hydrogenated graphene using non-equilibrium molecular dynamics simulations. It is found that the thermal conductivity greatly depends on the hydrogen distribution and coverage. For random hydrogenation, the thermal conductivity decreases rapidly with increasing coverage up to about 30%. Beyond this limit, however, the thermal conductivity is almost insensitive to the coverage. For patterned hydrogenation with stripes parallel to the heat flux, the thermal conductivity decreases gradually with increasing coverage from 0% to 100%. In contrast, when the stripe direction is perpendicular to the heat flux, a small (5%) coverage causes a sharp (60%) drop of thermal conductivity. The deterioration of thermal conductivity is due to the sp2-to-sp3 bonding transition upon hydrogenation, which softens the G-band phonon modes. Percolation theory can be used to explain the variation of thermal conductivity at different hydrogenation distributions and coverages. The applicability of the rule of mixtures in predicting the thermal conductivity is also discussed. The work suggests that hydrogenation is a possible route to tune graphene thermal conductivity and manage heat dissipation in graphene-based nanoelectronic devices.